Asphalt compositions and the preparation thereof

ABSTRACT

Asphalt compositions and methods of forming such are described herein. The asphalt compositions and methods of forming such are generally adapted to enable open air processing while producing asphalt compositions that exhibit properties capable of meeting SUPERPAVE™ specifications.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to co-pending U.S. Patent ApplicationSer. No. 60/619,191, filed on Oct. 15, 2004.

FIELD

Embodiments of the present invention generally relate to asphaltcompositions and methods of forming the same.

BACKGROUND

Unfortunately, asphalt processing may cause the release of byproducts,such as hydrocarbons, hydrogen sulfide, nitrogen oxide and carbonmonoxide, for example. These byproducts may be formed in a number ofways. For example, hydrogen sulfide (H₂S) may be formed as a result ofsulfur additions used during crude fraction processing or as a result ofsulfur present in the crude fraction being processed, such as sour crudefractions, for example.

Further, the Strategic Highway Research Program (SHRP) was establishedin 1987 to improve the performance and durability of United States roadsand to make those roads safer for both motorists and highway workers.One of the results of SHRP was the development of the SuperiorPerforming Asphalt Pavements (SUPERPAVE™) specifications for asphalts.The SUPERPAVE™ system specifies materials characterization techniquesand results thereof for the performance certification of asphalt.

By specifying acceptable limits for the characterization results, ratherthan any particular composition, the SUPERPAVE™ specifications arematerial independent. Thus, an end user can require that asphalt meets aparticular SUPERPAVE™ specification and be reasonably confident thatinstalled asphalt will perform satisfactorily, without regard to thespecific crude oil source or other compositional parameters. Suchspecifications enable control of asphalt characteristics, such asrutting, low temperature cracking and fatigue cracking, for example.

As a result, it is desired to develop an asphalt composition and methodof forming such that meets both EPA and SUPERPAVE™ specifications in acost-effective manner.

SUMMARY

Embodiments of the invention generally include asphalt compositions. Inone embodiment, the asphalt compositions generally include a baseasphalt, an emissions reducing additive, an acid and a polymer.

In another embodiment, the asphalt composition includes a base asphaltand a polymer. In addition, the asphalt composition is suitable forprocessing in open air vessels while maintaining suitablecharacteristics.

Embodiments of the invention further include method of forming asphaltcompositions. In one embodiment, the method generally includes blendingan acid with an asphalt to form an acid modified asphalt and blendingthe acid modified asphalt with a polymer to form the asphaltcomposition.

In another embodiment, the method generally includes blending an acidand an asphalt to form an asphalt composition, at least a portion of theblending occurring in the presence of an oxygen containing gas.

DETAILED DESCRIPTION Introduction and Definitions

A detailed description will now be provided. The appended claims definean invention, which for infringement purposes is recognized as includingequivalents to the various elements or limitations specified in theclaim. Depending on the context, all references below to the “invention”may in some cases refer to certain specific embodiments only. In othercases it will be recognized that references to the “invention” willrefer to subject matter recited in one or more, but not necessarily all,of the claims. Each of the inventions will now be described in greaterdetail below, including specific embodiments, versions and examples, butthe inventions are not limited to these embodiments, versions orexamples, which are included to enable a person having ordinary skill inthe art to make and use the inventions, when the information in thispatent is combined with available information and technology.

Various terms as used herein are shown below. To the extent a term usedin a claim is not defined below, it should be given the broadestdefinition persons in the pertinent art have given that term asreflected in printed publications and issued patents. To the extent thatranges of values are used in the claims or description below, it shouldbe understood that any upper limit, lower limit and/or points that lietherein may be independently combined to define an embodiment of theinvention.

As used herein, the term “crosslinking agent” refers to an additive usedto introduce mechanical links and/or chemical bonds to a chemicalcompound.

The term “asphalt” means any asphalt bottoms fi-action, as well asnaturally occurring asphalts, tars and pitches and may be usedinterchangeably herein with the term “bitumen.” The term “asphalticconcrete” means asphalt used as a binder with appropriate aggregateadded, typically for use as a paving material.

The term “bottoms fraction” refers to a crude fraction having a flashpoint of about 70° F. or greater.

The term “crude fraction” refers to any of the various refinery productsproduced from crude oil, either by atmospheric distillation or vacuumdistillation, including fractions that have been treated byhydrocracking, catalytic cracking, thermal cracking or coking and thosethat have been desulfurized.

The term “processing” is not limiting and includes agitating, mixing,milling, blending and combinations thereof all of which are usedinterchangeably herein. The processing occurs in one or more vessels,such vessels being known to one skilled in the art.

The dynamic shear stiffness is measured by the maximum temperature atwhich the shear stiffness modulus divided by the sine of the phase angleis at least 1.0 kPa measured on unaged binder or at least 2.2 kPameasured on a rolling thin film residue by a dynamic shear rheometer(e.g., AASHTO TP5-93 test.)

The storage stability is the measure of phase separation over aspecified time period, such as 2 to 3 days, for example, at a specifiedelevated temperature, such as 160° C., for example. The phase separationis measured by the continuity of a top portion and a bottom portion. Thephase separation is continuous if the temperature which corresponds to1.0 kPa binder stiffness from the top and bottom portions is within 2°C. (e.g., AASHTO TP5 test.)

The low temperature stiffness is measured by AASHTO TP1.

Embodiments of the invention described herein generally include asphaltcompositions and methods of forming the same.

The asphalt composition may include at least 80 wt. % base asphalt, atleast 90 wt. % base asphalt or at least 95 wt. % base asphalt, forexample.

The base asphalt may be any suitable petroleum asphalt, asphalticresidue or combinations thereof. The base asphalts may be obtained fromdeep vacuum distillation of crude oil, resulting in a bottom producthaving a desired viscosity or from a solvent deasphalting process of thecrude oil that yields a demetalized oil, a resin fraction, an asphaltenefraction or combinations thereof, for example. The crude oil may be anycrude oil, such as sweet crude, sour crude, heavy crude, light crude,aromatic crude, napthenic crude or combinations thereof for example.

Polymer modified asphalts generally exhibit higher viscosities andmelting points than asphalt compositions that do not include a polymer,for example. Therefore, the asphalt compositions described herein mayinclude from about 0.01 wt. % to about 15 wt. % polymer or from about0.01 wt. % to about 6 wt. % polymer, for example.

The polymer may include any suitable organic polymer or polymercontaining at least one unsaturated bond, for example. In oneembodiment, the polymer includes block copolymers and/or elastomericpolymers (e.g., butyl rubber, polybutadiene, polyisoprene,polyisobutene, ethylene/vinyl acetate copolymer, polychloroprene,polynorbornene, nylon, polyvinyl chloride, polyethylene, polystyrene,polypropylene, fluorocarbon resin, polyurethane, acrylate resin, such aspolyacrylate and/or methacrylate, phenolic, alkyd, polyester,ethylene-propylene-diene and copolymers of styrene and conjugateddienes, such as styrene-butadiene-styrene and styrene-butadiene rubber.)

The asphalt composition includes an acid. Such acid modification of theasphalt generally results in asphalt compositions that exhibit improvedlow temperature performance, for example. The asphalt compositionincludes less than about 5 wt. % acid and may include from about 0.01wt. % to about 4.5 wt. % acid, or from about 0.05 wt. % to about 2 wt. %acid or from about 0.1 wt. % to about 1 wt. % acid, for example.

The acid may be any suitable inorganic acid, organic acid orcombinations thereof. In one embodiment, the acid is mineral acid, suchas sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid orcombinations thereof. In one embodiment, the acid has an H₃PO₄equivalent concentration of greater than 100%. For example, the acid maybe polyphosphoric acid (H_(n+2)P_(n)O_(3n+1), wherein n is greater than1), which may have an 1H₃PO₄ of 115 or 117, for example. In anotherembodiment, the acid is superphosphoric acid (H_(3.3)P1.3O₅), having anH₃PO₄ of 105. Unlike phosphoric acid, superphosphoric and polyphosphoricacid are not water-based and exhibit very low to no corrosivity. Suchlow water content and corrosivity generally provides easierprocessability in hot asphalt.

The asphalt composition may further include additives, such assulfonating agents, crosslinking agents or combinations thereof, forexample. The asphalt composition may include from about 0.001 wt. % toabout 5 wt. % of total additives or from about 0.01 wt. % to about 3 wt.% of total additives, for example.

In one embodiment, the asphalt composition includes an emissionsreducing additive. The emissions reducing additive generally includes ametal oxide. In one embodiment, the metal oxide is a transition metaloxide, such as zinc oxide, copper oxide, iron oxide, aluminum oxide orcombinations thereof, for example.

The crosslinking agents may be activators (e.g., zinc oxide),accelerators, such as sulfur compounds (e.g., mercaptobenzotbizole(MBT)) or both accelerators and activators, such as a zinc salt of MBT,for example. In one embodiment, the crosslinking agent is a metal oxide.When used in conjunction with an emissions reducing additive, thecrosslinking agent may be the same metal oxide or a different metaloxide than the emissions reducing additive.

The additives may further include unsaturated functional monomers,unsaturated carboxylic acids, unsaturated dicarboxylic acids,unsaturated anhydrides, unsaturated esters, unsaturated amides orcombinations thereof, for example.

Unexpectedly, the asphalt compositions described herein are capable ofexhibiting superior properties, such as those mandated by the SUPERPAVE™specifications.

For example, the asphalt composition exhibits storage stability.

The asphalt composition further exhibits thermal cracking resistance.Thermal cracking resistance is generally determined by the lowtemperature stiffness of the composition.

The asphalt composition also exhibits rutting resistance. Ruttingresistance is generally determined by the Dynamic Shear Stiffness of thecomposition at elevated temperatures.

It is possible to adjust the physical properties of the asphaltcomposition by varying the amount of each element in the composition.

The asphalt compositions described herein are capable of formation inany manner known to one skilled in the art, while maintaining theirsuperior physical properties. However, such compositions are alsocapable of formation through open tank processes. Unexpectedly, when theemissions reducing additive is utilized, the asphalt composition may beblended in open air tanks without releasing unacceptable levels ofbyproducts. Further, the asphalt composition can be exposed to oxygencontaining gases at any point in the process without detrimentaleffects. In one embodiment, the asphalt composition is contacted withair for a time of at least 15 minutes (e.g., from about 15 minutes to anindefinite period of time, such as storage), or from about 30 minutes toabout 6 hours. In another embodiment, one or more of the mixing vesselsis sparged with an oxygen containing gas. For example, the vessel can besparged with air near the bottom of the vessel at a rate of from about20 to about 70 L/hr/kg or from about 20 to about 55 L/hr/kg, forexample.

Illustrative methods of forming such asphalt compositions are describedbelow, but in no way limit the methods that may be utilized to form suchcompositions. For example, in one embodiment, asphalt is heated in afirst mixing vessel to a temperature of from about 300° F. to 400° F.Upon heating, the polymer is introduced to the first mixing vessel toform an asphalt concentrate, which is blended in the presence of air.For example, the asphalt concentrate can be blended in an open airvessel for a time sufficient to provide adequate mixing, such as fromabout 5 minutes to about 2 hours. “Asphalt concentrate” refers to apolymer rich asphalt mixture, such as an asphalt mixture having fromabout 5 wt. % to about 12 wt. % polymer.

The asphalt concentrate may then be transferred to a second mixingvessel or remain in the first mixing vessel. At such time, additionalasphalt is added to the asphalt concentrate to form a dilute asphalt.The “dilute asphalt” generally has a lower polymer concentration thanthat of the asphalt concentrate, such as from about 0.1 wt. % to about 5wt. % polymer, or from about 0.1 wt. % to about 2 wt. % polymer. Thedilution asphalt can be the same, slightly different or completelydifferent asphalts. In this embodiment, the acid is added to the secondmixing vessel at the same time as the additional asphalt. The acid isadded in a timed release sufficient to avoid foaming, such as from about20 minutes to about 1 hour, for example.

Alternatively, the acid can be added to the asphalt concentrate prior tothe additional asphalt. In one embodiment, the acid is added to theasphalt prior the polymer and then the resultant concentrate is diluted.As described above, the acid can be added at any point in the processand to any vessel or conduit in the process. For example, the acid canbe added to a first or second mixing vessel or to a conduit operablyconnecting the first and second mixing vessels.

The additives can be added to any vessel at any time throughout theprocess. For example, metal oxides can be added to the first asphaltprior to polymer or acid addition. In one embodiment, elemental sulfur,in some instances functioning as a crosslinking agent, is added to theasphalt concentrate, either separate or at the same time as theadditional asphalt. In such an embodiment, the asphalt is contacted withsulfur in an environment capable of evacuating the sulfur compoundsemitted, such as H₂S, to emissions abatement.

In an alternative embodiment, the process may include forming a polymerfree asphalt composition, i.e., an asphalt composition includingessentially 0 wt. % polymer. In such an embodiment, the polymer additionstep is eliminated from the processes described herein.

Product Applications

The asphalt compositions described herein can be used for manyapplications, such as road paving, sealing, water proofing, asphaltcement and/or roofing, for example.

EXAMPLES Example 1

An asphalt composition (94.8 wt. % asphalt, 4.5 wt. %styrene-butadiene-styrene block copolymer, 0.2 wt. % zinc oxide, 0.1 wt.% sulfur, 0.1 wt. % MBT and from 0.3 to 0.6 wt. % polyphosphoric acid)was formed by the following:

Zinc oxide was added to asphalt stored in a vessel at 325° F. Superphosphoric acid was then added and the resultant compound was agitatedin the presence of air to form a substantially uniform mixture.

Such mixture was then pumped to a blending vessel and heated to atemperature of about 350° F. Styrene-Butadiene-Styrene block copolymerwas then added to the blending vessel to form an asphalt concentratemilled to disperse the polymer throughout the asphalt in the presence ofair. The resultant concentrate was then transferred to a closed blendingtank and diluted with additional asphalt to form a 4.5 wt. % polymersolution. Sulfur and MBT were then added to the asphalt mixture to formthe resulting asphalt composition.

Hypothetical Example 2

The same asphalt composition will be formed by the following:

Zinc oxide will be added to asphalt stored in a vessel at 325° F. Themixture will be agitated in the presence of air to form a substantiallyuniform mixture and heated to a temperature of about 350° F.Styrene-Butadiene-Styrene block copolymer (12 wt. %) will then be addedto the vessel and the concentrate milled to disperse the polymerthroughout the asphalt. The resultant concentrate will be diluted withadditional asphalt to form a 3 wt. % polymer solution. Sulfur and MBTwill then be added to the asphalt mixture prior to the addition of superphosphoric acid to form the resulting asphalt composition.

The asphalt composition will then be further diluted to form a 2 wt. %polymer modified asphalt (PMA) composition. The PMA will be combinedwith aggregate to form a paving composition.

1.-18. (canceled)
 19. An asphalt composition made by a plurality ofsteps comprising: heating a base asphalt to a temperature of from 300°F. to 400° F.; introducing a polymer to form an asphalt concentrate andblending the asphalt concentrate, wherein said concentrate has from 5wt. % to 12 wt. % of the polymer; adding zinc oxide before or after thepolymer and before any mineral acid, and further blending theconcentrated asphalt; adding a mineral acid, and further blending theconcentrated asphalt; and wherein at least a portion of one or more ofthe blendings after the zinc oxide addition occurs in the presence of anoxygen containing gas.
 20. The asphalt composition of claim 1, whereinthe asphalt concentrate is blended in the presence of air for from 5minutes to 2 hours.
 21. The asphalt composition of claim 19, furthercomprised of from 0.001 wt. % to 5 wt. % of additives selected from thegroup consisting of sulfonating agents, cross-linking agents, emissionsreducing additives, and combinations thereof and wherein said additivesare at least comprised of sulfur and mercaptobenzothizole (MBT).
 22. Theasphalt composition of claim 19, wherein additional base asphalt isadded to the concentrate to form a diluted asphalt, wherein the dilutedasphalt is comprised of at least 90 wt. % base asphalt, from 0.1 wt. %to 5 wt. % of the polymer, and from 0.01 wt. % to 2 wt. % of the acid.23. The asphalt composition of claim 19, wherein the acid is comprisedof polyphosphoric acid.
 24. The asphalt composition of claim 19, whereinthe acid is a phosphoric acid having a H₃PO₄ equivalent concentration ofgreater than 100%.
 25. The asphalt composition of claim 19, wherein thephosphoric acid is selected from polyphosphoric acid, superphosphoricacid and combinations thereof.
 26. The asphalt composition of claim 19,wherein the acid is comprised of sulfuric acid, nitric acid,hydrochloric acid, phosphoric acid or combinations thereof.
 27. Theasphalt composition of claim 19, wherein the polymer is milled todisperse the polymer throughout the asphalt, and wherein at least aportion of the milling occurs in the presence of air.
 28. An asphaltcomposition made by a plurality of steps comprising: heating a baseasphalt to a temperature of from 300° F. to 400° F.; introducing apolymer to form a polymer modified asphalt, and blending the polymerwith the asphalt, wherein said asphalt has from 0.1 wt. % to 5 wt. % ofthe polymer; adding zinc oxide before or after the polymer and beforeany acid addition, and further blending the asphalt; adding from 0.01wt. % to 2 wt. % of a mineral acid, and blending the asphalt; andwherein at least a portion of one or more of the blendings after zincoxide addition occurs in the presence of an oxygen containing gas, andwherein said polymer modified asphalt is comprised of at least 90 wt. %to 95 wt. % of asphalt.
 29. The asphalt composition of claim 28 whereinthe polymer modified asphalt is blended in the presence of air for from5 minutes to 2 hours.
 30. The asphalt composition of claim 28, furthercomprised of from 0.001 wt. % to 5 wt. % of additives selected from thegroup consisting of sulfonating agents, cross-linking agents, emissionsreducing additives, and combinations thereof, and wherein said additivesare at least comprised of sulfur and mercaptobenzothizole (MBT).
 31. Amethod of forming an asphalt concentrate comprising: heating a baseasphalt to a temperature of from 300° F. to 400° F.; adding zinc oxideand blending the asphalt and zinc oxide together, wherein the zinc oxideis added before or after a polymer and before any mineral acid, whereinzinc oxide is used as an additive for reducing hydrogen sulfideemissions, and wherein at least a portion of one or more of theblendings after zinc oxide addition occurs in the presence of an oxygencontaining gas; blending a mineral acid with an asphalt to form an acidmodified asphalt; blending the acid modified asphalt with a polymerselected from the group consisting of block copolymers, elastomericpolymers, or a combination thereof; and wherein the asphalt compositionis comprised of from 0.1 wt. % to 15 wt. % of the polymer, from 0.01 wt.% to less than 5 wt. % of the acid.
 32. The method of claim 31, whereinthe oxygen containing gas is air.
 33. The method of claim 31, furthercomprised of adding from 0.001 wt. % to 5 wt. % of additives comprisedof sulfur and mercaptobenzothizole (MBT) to the asphalt.
 34. The methodof claim 31, wherein additional base asphalt is added to form a moredilute asphalt that is used in an end use application.
 35. A method offorming an asphalt composition comprising: heating a base asphalt to atemperature of from 300° F. to 400° F.; blending a mineral acid and anasphalt to form an asphalt composition; adding zinc oxide to reducehydrogen sulfide emissions and blending the asphalt, wherein at least aportion of the blending after zinc oxide addition occurs in the presenceof an oxygen containing gas; and wherein the asphalt composition iscomprised of 0.01 wt. % to less than 5 wt. % of the acid.
 36. The methodof claim 35, wherein additional base asphalt is added to form a moredilute asphalt that is used in an end use application.
 37. The method ofclaim 35, wherein the oxygen containing gas is air.
 38. The method ofclaim 35, further comprised of adding from 0.001 wt. % to 5 wt. % ofadditives selected from the group consisting of sulfonating agents,cross-linking agents, emissions reducing additives, and combinationsthereof, and wherein said additives are at least comprised of sulfur andmercaptobenzothizole (MBT).
 39. The method of claim 35, furthercomprising blending 0.01 wt. % to 15 wt. % of a polymer with theasphalt, wherein the zinc oxide is added before or after the polymer.40. The method of claim 35, further comprising milling the polymer todisperse the polymer throughout the asphalt, wherein at least a portionof the milling occurs in the presence of air.
 41. The method of claim35, wherein a mixing vessel is sparged with air at least during aportion of the blending.
 42. The method of claim 35, wherein the acid isadded in a timed release manner over a period of from 20 minutes to 1hour to prevent foaming.
 43. The method of claim 35, further comprisingthe step of adding aggregate to the asphalt.
 44. The method of claim 38,wherein the sulfonating agents and/or cross-linking additives are mixedwith the asphalt in a closed blending tank.